Reassessing Transketolase Assays: Methodological Considerations for Detecting Functional Thiamine Deficiency

Area of Science:

• Biochemistry
• Nutritional Science
• Enzymology

Background:

• Thiamine (vitamin B1) deficiency is a widespread issue in humans and animals.
• Thiamine diphosphate (TDP) is a crucial cofactor for metabolic enzymes, notably transketolase (TKT).
• TKT is a rate-limiting enzyme in the pentose-phosphate pathway, essential for cellular metabolism.

Purpose of the Study:

• To review preanalytical variables, assay methodologies, and data presentation for TKT measurements.
• To explore the utility of TKT assays beyond deficiency screening, focusing on enzyme function and cofactor dependence.
• To provide an improved framework for interpreting TKT measurements as indicators of functional thiamine status.

Main Methods:

• Evaluation of erythrocyte and tissue TKT activity measurements in human and nonhuman studies.
• Analysis of strategic variations in assay conditions (e.g., TDP concentration, magnesium presence) to assess TKT function.
• Review of factors influencing measured TKT activity and responsiveness.

Main Results:

• TKT activity assays, with or without exogenous TDP, provide a functional assessment of thiamine utilization.
• Assay condition modifications can differentiate true thiamine deficiency from impaired enzyme utilization or altered enzyme properties.
• Understanding biological and methodological determinants is key to accurate TKT activity interpretation.

Conclusions:

• TKT assays offer a valuable, functional measure of thiamine status, complementing direct thiamine quantification.
• Strategic assay design and interpretation frameworks can enhance the diagnostic utility of TKT measurements.
• Expanded application of TKT assays can benefit clinical, translational, and ecological studies of thiamine status.